Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Suburban, and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0125 is designed to detect a skewed ECT sensor or a faulty thermostat.
Excessive coolant flow through the by-pass hose to the throttle body may cause this DTC to set.